A Level Biology Revision Notes

Comprehensive A Level Biology revision notes providing information and assistance for all UK examination boards (AQA, OCR, Edexcel) as well as international curriculum (CIE).

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Plant Hormones

Introduction Coordination of all the activities taking place within an organism is essential for the maintenance of life. This coordination among various cells of the body can be achieved in two ways; nervous coordination and chemical coordination. Chemical coordination is brought about by hormones. Hormones are the chemical substances capable of affecting the various chemical …

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Nitrogen Cycle

Introduction Nitrogen is the most abundant gas present in our atmosphere. It makes more than 70% of the gases present in the atmosphere of our planet. Being a component of organic compounds like proteins and nucleic acids, nitrogen is an important nutrient required for the normal growth and development of living organisms. The nitrogen cycle …

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Nutrient Loss

Introduction Nutrients are needed by organisms for their normal growth and development. Most of the organisms obtain nutrients from the surrounding environment. Animals get most of the nutrients in the form of food and air. Plants obtain nutrients present in the soil as well as air. The conservation of nutrients in the environment is essential …

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Nutrient Recycling

Introduction Nutrients are the substances that are required by organisms for growth and development. A nutrient is defined as any substance that provides nourishment to the body and is essential for normal growth and development, reproduction, and survival of the organism. All the organisms obtain nutrients from the environment surrounding them. The total amount of …

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Synthesis of Organic Compounds

Introduction Organic compounds are those that are made up of carbon and hydrogen (hydrocarbons) and their derivatives. Organic compounds are the most widely spread chemical species present on earth. They are the molecules of life. All the life on this planet is dependent on various organic compounds found in the living systems. It was thought …

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Tropism

An introduction to Tropism Most of the time when we think about a living organism the first thought our mind gives birth to is the idea of movement. If something (the biotic object) is performing an act of movement it is pronounced living. All living beings exhibit some sort of motion. This motion or movement …

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Eutrophication

The literal meaning of the eutrophication is “well-nourished”. But this term brings a negative connotation when it is studied in the field of ecology and environmental sciences. Eutrophication is a situation in which an excessive growth of organisms on the surface of an aquatic body is observed due to the presence of an excessive amount …

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Depolarization

Introduction All the living cells are electrically neutral with having an equal number of positive and negative charges. The cells try their best to maintain this electrical neutrality. The cytoplasm of the cells contains different positive and negative species such as inorganic ions, organic ions, acids, proteins, etc. The concentration of all these substances is …

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Myelin Sheath

Introduction Neurons are the structural and functional units of the nervous system found in animals. They are responsible for bringing about the nervous coordination among the various organs found in the body. each neuron has a cell body and cellular processes. The cellular processes of neurons are interconnected via synapses. The information is carried by …

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Oligodendrocytes

Introduction All the organs found in multicellular organisms are made up of two types of cells; parenchymal cells and the supporting cells. The parenchymal cells are involved in performing the main function of that organ such as nephrons in kidneys and myocytes in the heart, etc. The supporting cells are responsible for maintaining the structure …

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